Sprinkle gelatin over cold water; let stand 5 minutes.
Combine egg yolks, 1/4 cup sugar, 3/4 cup pineapple, lemon rind, and juice in top of a double boiler. Place over boiling water and cook, stirring constantly, until smooth and thickened. Add softened gelatin; stir until gelatin is dissolved. Remove from heat and cool.
Beat egg whites (at room temperature) and salt until soft peaks form. Gradually add remaining sugar, beating until stiff peaks form. Fold into pineapple mixture. Spoon into tart shells; chill. Garnish with whipped cream and remaining pineapple.